Question

For which colour of white light, the refractive index of a transparent medium is least ?

• A. Green
• B. Red
• C. Blue
• D. Black

Answer 1

The correct option is B Red

Red light has the maximum wavelength $\lambda$ and frequency $f$ of light doesn't change in any medium. Thus, red light travels fastest through a medium since $v=f\lambda$
According to Snell's law $nv$ is constant for all the constituents of a single wave passing through a particular medium, here the seven wavelengths of white light. Since velocity $v$ of red light through a medium is maximum, refractive index $n$ for red light will be least.